How to Identify Paddlefish

To identify Paddlefish (Polyodon spathula), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

Dorsally olive green to grayish-blue, fading to a lighter, almost white ventral surface. The skin is smooth and lacks scales, except for a few ganoid scales on the caudal peduncle and upper lobe of the caudal fin in juveniles, which are lost in adults.

Scale type

none

Mouth position

inferior

Distinctive features

Long, flattened, paddle-shaped rostrum (snout) that can be up to one-third of its body length., Large, wide mouth located ventrally, adapted for filter feeding., Small, widely spaced eyes located at the base of the rostrum., Lack of scales (except for vestigial scales on the caudal peduncle in juveniles)., Heterocercal caudal fin (upper lobe longer than the lower).

Dorsal fin

Single, posterior dorsal fin, soft-rayed.

Tail fin

Strongly heterocercal, deeply forked, with the upper lobe significantly longer than the lower.

Pectoral fin

Large and triangular, positioned low on the body.

Distinctive fins

Pelvic fins are abdominal. All fins are soft-rayed.

Identification Tips

1. 1

   Rostrum

   The most distinguishing feature is the long, flattened, paddle-shaped snout, which is unique among North American freshwater fish. It is covered with electroreceptors used to detect zooplankton.

2. 2

   Body covering

   Adult paddlefish have smooth, scaleless skin, unlike most other fish. Juvenile paddlefish may have a few ganoid scales on the caudal peduncle.

3. 3

   Mouth

   Possesses a very large, wide, terminal mouth that is opened while swimming to filter feed. This is distinct from the subterminal, protrusible mouth of sturgeons.

4. 4

   Gills

   Has long, fine gill rakers adapted for filtering small organisms from the water.

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